Method and apparatus for detecting absolute value amplitude of am suppressed carrier signals

Claim 2

In a signal detecting circuit for detecting the amplitude envelope of a modulated carrier which is amplitude modulated with an information signal, means responsive to said modulated carrier and a first reference carrier to provide a first signal representing a vector component of the instantaneous amplitude of the information signal, means responsive to said modulated carrier and a second reference carrier to provide a second signal representing a further vector component of the instantaneous amplitude of the information signal, first means for combining the first and second signals to provide an output signal representing the vector sum of said first and second signals, and second means responsive to said output signal to provide a signal which is proportional to the absolute value amplitude of the information signal.

Claim 3

A signal detecting circuit as set forth in claim 1 which includes reference carrier means for providing first and second reference carriers which are of the same frequency as the modulated carrier.

Claim 4

A signal detecting circuit as set forth in claim 1 which includes reference carrier means for providing first and second reference carriers which are of a predetermined frequency which is different from the frequency of said modulated carrier.

Claim 5

In a signal detecting circuit for detecting the amplitude envelope of a modulated carrier which is amplitude modulated with an information signal, reference carrier means for providing quadrature phases of a reference carrier, first product detector means responsive to said modulated carrier and a reference carrier of a first phase provided by said reference carrier means to provide a first signal representing a first vector component of the amplitude of the information signal, second product detector means responsive to said modulated carrier and a reference carrier of a second phase provided by said reference carrier means to provide a second signal representing a second vector component of the amplitude of the information signal, and output means including first means for providing an output signal representing the vector sum of the first and second signals provided by said first and second product detector means and second means responsive to said output signal to provide a signal proportional to the absolute value amplitude of the information signal.

Claim 6

In a signal detecting circuit for detecting the amplitude envelope of a modulated carrier which is amplitude modulated with an information signal, reference carrier means for providing quadrature phases of a reference carrier, first product detector means responsive to said modulated carrier and a reference carrier of a first phase provided by said reference carrier means to provide a first signal representing a first vector component of the amplitude of the information signal, second product detector means responsive to said modulated carrier and a reference carrier of a second phase provided by said reference carrier means to provide a second signal representing a second vector component of the amplitude of the information signal, and output means including first means for providing an output signal representing the vector sum of the first and second signals provided by said first and second product detector means and second means responsive to said output signal to provide a signal proportional to the absolute value amplitude of the information signal.

Claim 7

A signal detecting circuit as set forth in claim 4 wherein said reference carrier means includes signal generating means for providing a reference carrier of the same frequency as the frequency of the modulated carrier.

Claim 8

A signal detecting circuit as set forth in claim 4 wherein said first means includes first analog multiplier means responsive to said first signal to provide a signal representing the square of the value of said first component of the amplitude of the information signal, and second analog multiplier means responsive to the second signal to provide a signal representing the square of the value of the second component of the amplitude of the information signal, and summing means for summing the signals provided by said first and second analog multiplier means, and wherein said second means includes means for obtaining the square root of the sum of the signals provided by said first and second analog multiplier means.

Claim 9

In a signal detecting circuit for detecting the amplitude envelope of a modulated carRier which is amplitude modulated with an information signal, reference carrier means for providing quadrature phases of a reference carrier, first product detector means responsive to said modulated carrier and a reference carrier of a first phase provided by said reference carrier means to provide a first output signal representing a first vector component of the amplitude of the information signal, second product detector means responsive to said modulated carrier and a reference carrier of a second phase provided by said reference carrier means to provide a second output signal representing a second vector component of the amplitude of the information signal, further reference carrier means for providing quadrature phases of a further reference carrier, first modulator means for amplitude modulating a reference carrier of a first phase provided by said further reference carrier means with the first output signal to provide a first amplitude modulated signal which is related to the amplitude of the information signal, second modulator means for amplitude modulating a reference carrier of a second phase provided by said further reference carrier means with the second output signal to provide a second amplitude modulated signal which is related to the amplitude of the information signal, summing means for summing the amplitude modulated signals provided by said first and second modulator means to provide a signal representing the vector sum of the first and second output signals provided by said first and second product detector means, respectively, and demodulating means for demodulating the signal provided by said summing means to provide a signal proportional to the absolute value of the amplitude of the information signal.

Claim 10

In a signal detecting circuit for detecting the amplitude envelope of a modulated carRier which is amplitude modulated with an information signal, reference carrier means for providing quadrature phases of a reference carrier, first product detector means responsive to said modulated carrier and a reference carrier of a first phase provided by said reference carrier means to provide a first output signal representing a first vector component of the amplitude of the information signal, second product detector means responsive to said modulated carrier and a reference carrier of a second phase provided by said reference carrier means to provide a second output signal representing a second vector component of the amplitude of the information signal, further reference carrier means for providing quadrature phases of a further reference carrier, first modulator means for amplitude modulating a reference carrier of a first phase provided by said further reference carrier means with the first output signal to provide a first amplitude modulated signal which is related to the amplitude of the information signal, second modulator means for amplitude modulating a reference carrier of a second phase provided by said further reference carrier means with the second output signal to provide a second amplitude modulated signal which is related to the amplitude of the information signal, summing means for summing the amplitude modulated signals provided by said first and second modulator means to provide a signal representing the vector sum of the first and second output signals provided by said first and second product detector means, respectively, and demodulating means for demodulating the signal provided by said summing means to provide a signal proportional to the absolute value of the amplitude of the information signal.

Claim 11

A detecting circuit as set forth in claim 7 wherein said demodulating means includes amplitude demodulator means having a first input connected to the output of said summing means to receive a signal representing the vector sum of the product demodulator outputs provided by said summing means and limiter means having an output connected to a second input of said amplitude demodulator means for supplying to said amplitude demodulator means a constant amplitude signal of the same phase and frequency as the signal supplied to said amplitude demodulator means by said summing means.

Claim 12

A signal detecting circuit as set forth in claim 8 which includes first rectifier means interposed between said first product detector means and said first modulator means, second rectifier means interposed between said second product detector means and said second modulator means, said first and second rectifier means being operable to limit the amplitude modulation provided by said first and second modulator means to less than or equal to 100 percent.

Claim 13

In a signal detecting circuit for detecting the amplitude envelope of an amplitude modulated suppressed carrier, reference carrier means for providing quadrature phases of a reference carrier, first product detector means responsive to the modulated carrier signal and a zero degree phase reference carrier provided by said reference carrier means to provide a first signal A(t) cos theta , where A(t) represents the amplitude of the information signal and theta represents the phase angle between the modulated carrier and the reference carrier, second product detector means responsive to the modulated carrier and a ninety degree phase reference carrier provided by said reference carrier means to provide a second signal A(t) sin theta , and output means including first means for combining said first and second signnals to provide an output signal representing the vector sum of said first and second signals, and second means responsive to said output signal to provide a signal K A(t) , which is proportional to the absolute value amplitude of the information signal.

Claim 14

In a signal detecting circuit for detecting the amplitude envelope of an amplitude modulated suppressed carrier, reference carrier means for providing quadrature phases of a reference carrier, first product detector means responsive to the modulated carrier signal and a zero degree phase reference carrier provided by said reference carrier means to provide a first signal A(t) cos theta , where A(t) represents the amplitude of the information signal and theta represents the phase angle between the modulated carrier and the reference carrier, second product detector means responsive to the modulated carrier and a ninety degree phase reference carrier provided by said reference carrier means to provide a second signal A(t) sin theta , and output means including first means for combining said first and second signnals to provide an output signal representing the vector sum of said first and second signals, and second means responsive to said output signal to provide a signal K A(t) , which is proportional to the absolute value amplitude of the information signal.

Claim 17

A method as set forth in claim 11 wherein the step of combining the first and second signals includes obtaining the square of the first and second signals to provide third and fourth signals, and obtaining the square root of the sum of the third and fourth signals.

Claim 18

The method as set forth in claim 11 wherein the step of combining the first and second signals includes using the first and second signals to amplitude modulate quadrature phases of a further reference carrier to provide first and second amplitude modulated signals, combining the first and second amplitude modulated signals, and demodulating the sum of the first and second amplitude modulated signals.

Claim 19

A method as set forth in claim 13 wherein the step of demodulating the sum of the first and second amplitude modulated signals includes deriving from the sum of the first and second amplitude modulated signals a constant amplitude reference signal of the same frequency and phase as the amplitude modulated signals, and using the constant amplitude reference signal to recover the amplitude information from the sum of the first and second amplitude modulated signals.